Effect of Different Heat Treatments on the Structure and Processing Properties of Buffalo Milk Casein
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Abstract:
The non-heat-treated buffalo milk casein was used as a control to investigate the effects of four common heat treatments on the structure of buffalo milk casein. The results showed that macromolecular polymers were produced by heating and were mainly formed by proteins linked by disulfide bonds. After the heat treatment of 80 ℃, buffalo milk casein had the highest foaming capacity (FC) and foaming stability (FS) at 137.33% and 32.33%, respectively. After ultra-high temperature sterilization (135 ℃), the buffalo milk casein enlarged significantly to 516.2 nm, with destroyed casein micelles and an altered surface structure. Heat treatments modified the secondary structure of casein; notably, at 135 ℃, the α-helix and β-sheet contents decreased significantly, with minimum values of 13.76% and 35.84%, respectively. Heat treatments also altered the tertiary structure and surface hydrophobicity of casein; the pasteurized milk (80 ℃) had the highest fluorescence intensity at 582.44, and the ultrahigh-temperature sterilized milk had the highest surface hydrophobicity at 258.96. These results indicated that pasteurization has a relatively small effect on casein, while the ultra-high temperature condition tends to cause protein aggregation, affecting product stability. Therefore, 80 ℃ is an optimal temperature for the heat treatment of buffalo milk. The findings of this study provide a theoretical basis for improving the stability of buffalo dairy products in the production process.
